Mars, one rover at a time

Sojourner (1997): proof that wheels work

Mars Pathfinder landed on 4 July 1997 and released Sojourner, the first rover on Mars, about the size of a microwave oven. The lander came down on a parachute and rockets, then on airbags that inflated about 100 metres above the ground; it bounced more than fifteen times before it came to rest.

Spirit and Opportunity (2004): following the water

The twin rovers landed in January 2004: Spirit in Gusev Crater on 3 January, Opportunity at Meridiani Planum on 24 January. Both used airbags, like Pathfinder.

By reading the rock record, the two rovers confirmed that water once lasted on the surface of Mars. Spirit ended its mission in 2010. Opportunity last spoke to Earth on 10 June 2018, when a planet-wide dust storm covered its solar panels; by then it had driven 45.16 kilometres.

Curiosity (2012): the sky crane

Curiosity did not use airbags. It landed in Gale Crater on 6 August 2012 (Eastern time; 5 August in California) with a new system, the sky crane: a descent stage with eight rocket engines lowered the rover on a 7.5-metre bridle, then flew away once the wheels touched the ground.

Perseverance (2021): samples and a helicopter

Perseverance landed in Jezero Crater on 18 February 2021 with the same sky crane, plus new tools for choosing a safe spot during descent. Its work has four parts: the geology of the crater, the search for signs of past microbial life, caching rock samples for possible future return to Earth, and testing technology for human explorers.

It carried Ingenuity, a 1.8-kilogram helicopter. On 19 April 2021 Ingenuity became the first aircraft to make a powered, controlled flight on another planet. In October 2026 Perseverance passed Opportunity’s record for the longest drive on another world.

Seven minutes of terror

Entry, descent and landing takes about seven minutes, in which the spacecraft slows from roughly 21,000 km/h to zero. Radio signals need several minutes to cross the distance to Earth, so every step has to run on its own. During Perseverance’s landing, the signals took 11 minutes to reach the control room at JPL. More on that delay in How a mission flies.